Polyolefins, as a class of materials, have relatively poor adhesion and compatibility with more polar polymeric materials. In most cases, a separate adhesive is required in order to adhere polyolefins to polar substrates like polyesters, polyamides, polyurethanes, and the like. Similarly, a third component compatibilizer typically has to be used to prepare satisfactory melt blends of polyolefins with other more polar thermoplastics.
Typically, anhydride grafting onto polyolefins is used to provide some level of compatibility and/or adhesion to more polar substrates, however, this functionality is not optimum for adhesion in many cases. In particular, strong adhesion to polyurethane (PU) substrates is achieved if covalent bonds can be formed across the interface of a polyolefin-polyurethane structure. Adhesion to PU substrates can be improved using a polyolefin with functional groups that can react with urethane linkages and/or terminal isocyanate groups. Attempts have been made to incorporate amine functionality and/or hydroxyl functionality into a polyolefin, by reacting primary diamines or alkanolamines with anhydride grafted polyolefins. However, it has been difficult to prepare such functional polymers, since the unreacted amine groups and unreacted hydroxyl groups of the imide can further react with anhydride to form branched and crosslinked structures in the final polymer product. In addition, such reactions typically required the initial formation and isolation of an anhydride grafted polyolefin, prior to the reaction with the functionalization agent (diamine or alkanolamine). Thus the separate formation and isolation of the graft precursor adds additional processing costs to the functionalization reaction.
U.S. Pat. No. 5,424,367 and U.S. Pat. No. 5,552,096 and U.S. Pat. No. 5,651,927 disclose sequential reactions in one extruder for the functionalization of a polymer. Each reaction zone has means for introduction of reagents, for mixing of reagents with polymer and for removal of by/co-products or unreacted reagents. These patents do not disclose the use of primary-secondary diamines to reduce competing crosslinking reactions.
International Publication No. WO 93/02113 discloses (1) graft polymers comprising reactive amine functionality that are prepared by reacting a thermoplastic polymer, comprising at least one electrophilic functionality sufficient to react with primary amino groups, and (2) a compound comprising a primary amine and a secondary amine, the secondary amine having reactivity approximately equal to, or less than, the primary amine. However, this reference does not disclose a subsequent in-situ functionalization of a grafted polyolefin, without the prior isolation of the grafted polyolefin.
Additional functionalization reactions are disclosed in U.S. Pat. No. 6,469,099 B1; U.S. Pat. No. 5,599,881; U.S. Pat. No. 5,886,194; U.S. Pat. No. 4,137,185; U.S. Pat. No. 4,374,956; U.S. Pat. No. 3,471,460; U.S. Pat. No. 3,862,265; U.S. Publication No. US 20060025316; European Application No. 0 634 424 A1; European Application No. 0 036 949 A; International Publication No. WO 01/29095; International Publication No. WO 06/039774; and in the following references, “Melt Amination of Polypropylenes,” Q. W. Lu et al., Journal of Polym. Sci.-Polym. Chem. 43, 4217 (2005); “Reactivity of Common Functional Groups with Urethanes,” Q. W. Lu et al., Journal of Polym. Sci.-Polym. Chem., 40, 2310 (2002); and “Melt Grafting of Mateamic Acid onto LLDPE,” A. E. Ciolino et al., Journal of Polym. Sci.-Polym, Chem., 40, 3950 (2002).
However, these references do not disclose amine functionalized and hydroxyl functionalized polyolefins that can be prepared in a low cost manner, without producing significant amounts of branching and crosslinks in the final polymer product. There is a need for an in-situ preparation of amine functionalized or hydroxyl functionalized polyolefin that does not require the initial formation and isolation of a graft polyolefin precursor, and that does not result in the formation of significant branching and crosslinking in the functionalized polyolefin. Moreover, there is a need for an amine-functionalized polyolefin that provides enhanced compatibility and/or adhesion to polyurethane substrates. These needs and others have been met by the following invention.